Tourists believed to be among dead and injured after New Zealand volcano erupts

Authorities say the death toll is expected to rise after about 50 people, many of whom are tourists, were caught up in a volcano eruption on New Zealand's Whakaari island.

At least five people have died and 23 have been rescued so far, some of whom are reported to be critically ill.

The remainder are currently unaccounted for after the sudden explosion on Monday afternoon (approximately Monday 1am UK time), which hurled ash and rock high into the air and created a thick plume of smoke.

New Zealand prime minister Jacinda Ardern said tour groups, both from New Zealand and overseas, had been on the island at the time. She assured relatives the police are 'doing everything they can'.

More than 20 Australians are believed to be among the tourists. Some of the tourists are believed to be passengers on the Royal Caribbean cruise ship Ovation of the Seas, according to the New Zealand Cruise Association.

The eruption happened about 2pm local time, 48km off the coast of the Bay of Plenty, on the North Island.

Search teams have not yet been able to land on Whakaari, which is also known as White Island, because it is still considered too dangerous, according to reports.